As a note, I have *once* managed to get identd to fail in 7.17. It was when reconnecting after a ping timeout. The first reconnect attempt gave me "too many connections from your host" error and disconnected me immediately. The identd worked fine on that reconnection attempt. However, the next attempt (after a few servers gave me connection timed out errors) did not respond to identd. It was requested, but my computer didn't respond.
Now... before assuming this has anything to do with the topic here, this has happened off and on for many versions of mIRC and is probably related to just timing out sending the identd response. If I already pinged out, then it isn't too hard to imagine the identd timing out as well. It's possible there is a bug that's causing that, but if there is, it doesn't manifest itself very often.
So far, that is the only time I have gotten it to fail on 7.17.